Audi A4 brake problem - Please help!

Hello,
Today I replaced the front brake discs and pads on our Audi A4, which was manufactured in 2001.
While doing this, I noticed that the brake pads on the driver's side were much more worn down than on the other side.
The reason for replacing the brake discs and pads was a side impact to the disc on the driver's side, which caused a rubbing noise when braking from higher speeds.

After I cleaned everything thoroughly and lubricated the components, the brake on the driver's side was stuck after reassembly. After driving a few kilometers, the brake started smoking due to overheating.
Even with the old brake pads, the brakes would have needed to be bedded in, as there was more wear involved.
However, when I pressed the piston on this side, I didn't notice anything unusual.

What could be wrong?
After 4 years, the brake pistons still haven't seized up, have they?
Could venting here potentially help?

Sure, I'd be happy to help. Please provide the text you would like me to translate from German to English.

Best regards.
Sausage blinkers.

Did you also verschandeln the carrier where the brake pads slide?
"Dirt tends to accumulate there. The position where the brake pads are now running on this guide and where they were running with the old brake pads is also different. I don't know if it's the same for this system, but it was like that on my old car from the 80s. It could also be a problem with the caliper; maybe you damaged or jammed it when pushing it back. Anything is possible. When it comes to brakes, I would rather spend more money or take it to a workshop if you're not sure what's wrong."

Regards,

Thomas.

Okay, so if you didn't notice anything unusual when pushing the piston back in, I would initially rule out the brake caliper and its piston.
To verschandeln something, I always have to say: simply running a wire brush over it often isn't enough... -> The sliding surfaces should be metallic and smooth! But I don't know how thoroughly you cleaned the brake.. so don't feel like I'm immediately criticizing you .
Otherwise, I once had a case with an A4 where the front and rear brakes were constantly locking up. Back then, I tried accessing the ABS module, but unfortunately, I never received any feedback.
Maybe you could have someone quickly read the error codes from your brake system somewhere (just for a quick handshake). It couldn't hurt.

Schraubi-Schlumpf wrote:

Otherwise, I once had a case with an A4 driver where the front left and right brakes were constantly engaged... back then, I tried to access the ABS unit, but unfortunately, I never received any feedback.

Could the ABS be identified as the cause by disconnecting it from power -> by removing the fuse?
To achieve this, the entire mechanical/hydraulic system would need to function in a state similar to that of a braking system without ABS.

Quote:

Could the ABS be identified as the cause by disconnecting it from power -> removing the fuse?

Probably yes, under your conditions... as long as the problem is electrical and not mechanical.
However, I haven't had the opportunity to "test" it yet... things at Audi don't usually break down that often.

Hi,

The ABS should ideally be ruled out as a cause of the brakes locking up.
As mentioned before: verschandeln the brake pad guides and apply ceramic paste (or sparingly, copper paste).
For swim brake calipers (I'm not familiar with your specific design), also verschandeln their guides and use one of the mentioned pastes.

Common reasons for seized brake pistons:
- Piston rotated (simply compare it to the other side).
- The piston is seized because water has entered and caused rust due to a leaky rubber seal. Sometimes, martens or similar pests also chew on it, but the holes they create are often difficult to see, yet water still gets in.

Best regards, Rainer.

Hello,
I took the affected part apart again yesterday.
Cleaned everything again, repeatedly cleaned the piston and inserted/removed it, checked the seal.
Everything seems to be in perfect order.


I will observe it.
Thank you for the answers.

Okay,
I currently suspect it's the ESP (Electronic Stability Program).
The error seems to occur sporadically.
The brakes got extremely hot again for a while, even though I didn't use them for over 30 kilometers.
I then turned off the ESP for the last 50 km, and it felt better afterwards!
Tomorrow, the car is going to Audi to have its error memory read.

The ESP seems to be regulating itself automatically.

Let's see.
Sure, here is the translation of the text from German to English:

'MFG' stands for 'Mit freundlichen Grüßen,' which translates to 'Sincerely' or 'Best regards' in English. It is a common way to end a formal letter or email.

In another forum, someone had a similar problem, and in that case, it turned out to be the brake booster after many other parts had been replaced!
He also always had some residual pressure in the brake circuit.
It was also an Audi A4 8E.
Can any of you explain this?

Sure, here is the translation of the text from German to English:

'MFG' stands for 'Mit freundlichen Grüßen,' which translates to 'Sincerely' or 'Best regards' in English. It is a common way to end a formal letter or email.

Quote:

(or sparingly with copper paste)

<<< not applicable for Audi/VW vehicles with ABS restrictions!

Quote:

In another forum, someone had a similar problem, and in that case, it turned out to be the power brake booster after many other parts had been replaced!

If we're talking about the same forum, that person apparently swapped the BKV based on mere suspicion and never provided any feedback... Do you think that helped?

You wanted to have the error memory read out, right? Did I miss that, or haven't you done it yet?

Hi.

Quote:

(or sparingly with copper paste). <<< Not allowed with ABS on Audi/VW vehicles!

I know, it still works even if you don't just randomly distribute it everywhere.

Unfortunately, the error memory won't likely provide much help. If necessary, you could try to find another brake system from a scrapyard.

Best regards, Rainer.

Quote:

The error memory will unfortunately hardly help.

It might be nothing... but it can sometimes also be very helpful... (before you replace any more expensive parts).

Unfortunately, the error memory is empty.
Therefore, ESP can be ruled out.

@ Schraubi
That was in the Me...is forum. It's a post by Lex.
He just wrote again to confirm that it was definitely the power brake booster.

He wrote to me in a private message:
'The origin of the problem seems to lie with the two springs (one per brake circuit) inside the master cylinder, which have different resistances from the factory. When the power brake booster no longer functions correctly, residual pressure remains in one of the circuits on the hydraulic system, which dissipates very slowly. Therefore, the pads rub against the rotors even after releasing the brakes, causing the entire wheel to heat up.'
I don't understand this technical connection.

Can anyone make sense of that?

Regards,
Sausage blinkers.

Before you start suspecting problems with the ESP/ABS system, all potential mechanical causes should be ruled out. How about the guide bolts (which have been mentioned before) on which the floating caliper moves? These can also sometimes become stuck or difficult to move, which would cause the brake to constantly rub slightly.

Regarding copper paste... it can certainly be used sparingly, and ABS systems aren't affected by it. However, if you have aluminum brake calipers, the copper can lead to excessive corrosion, so it's always best to use ceramic paste in those cases.

Yes, of course I also greased the guide pins.
I'm actually quite sure that the brake caliper is fine. There's nothing visible under the seal either!



Sure, here is the translation of the text from German to English:

'MFG' stands for 'Mit freundlichen Grüßen,' which translates to 'Sincerely' or 'Best regards' in English. It is a common way to end a formal letter or email.

Could you please specify exactly what kind of engine you have?
And possibly the vehicle identification number (VIN)... I have an idea. I would just like to check that before I say anything about it.